Field of the Invention
The present invention relates to an apparatus and method for activating a catalyst of a hybrid vehicle. More particularly, the present invention relates to an apparatus and method for activating a catalyst of a hybrid vehicle in which an exhaust gas is reflowed into a cylinder by opening an exhaust valve during a suction stroke in a regenerative braking condition and increasing temperature of exhaust gas.
Description of Related Art
Generally, a hybrid vehicle, in which a motor of an electric vehicle is applied to an existing internal combustion engine, or a combination of two or more driving sources such as a combination of an internal combustion engine and a fuel cell is applied, is recognized as a vehicle which is eco-friendly and has many improved factors in terms of fuel efficiency and performance as compared with existing vehicles.
Recently, as environmental problems have become an important issue, interest in methods of efficiently processing exhaust gas of the vehicle has increased.
Even in the hybrid vehicle, a catalyst is used in order to reduce the exhaust gas of the engine, but since an activated temperature of the catalyst is significantly higher than room temperature, the catalyst temperature is increased by driving the engine and thus the catalyst is activated.
In this case, in order to decrease kinetic energy among energy generated in the engine and increase heat energy, it is beneficial to sufficiently retard injection of fuel.
However, in this process, the retarded injected fuel is not used for generating driving power and but is used for increasing temperature of exhaust gas. Therefore, there is a problem that fuel consumption is increased.
Further, since temperature of an exhaust gas is very low or heat by combustion is not generated under a regenerative braking condition (for example, a coasting condition or a braking condition), the temperature of the exhaust gas exhausted through an exhaust system is low. Accordingly, it is difficult to increase temperature of the catalyst and the purification rate of the exhaust gas is decreased.
Particularly, since the exhaust gas is expelled after external air is sucked without combustion of fuel when the vehicle is driven under a fuel-cut mode (for example, an overrun condition), temperature of the exhaust gas is low. Therefore, the catalyst heated by heat of the exhaust gas under an initial cold starting condition is cooled by the exhaust gas having a low temperature when the vehicle is driven under the fuel-cut mode. Accordingly, the purification rate of the exhaust gas by the catalyst is decreased.
Further, when the vehicle travels, fuel injection and fuel-cut are frequently generated according to a driving condition. Since it is difficult to increase temperature of the catalyst when the injection of fuel is cut off, the purification rate of the exhaust gas by the catalyst is decreased.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.